1. Field of Invention
The present invention relates to semiconductor integrated circuits, and more specifically, to a low voltage reference circuit that is capable of outputting a plurality of voltages with minimal operating voltage overhead.
2. Description of Related Art
In many devices that incorporate analog, digital, and/or mixed-signal integrated circuits, voltage reference circuits are of critical importance to the proper functioning of the device. For example, circuits such as oscillators, Phase Locked Loops (PLLs), Digital-to-Analog Converters (DACs), and Analog-to-Digital Converters (ADCs), depend on stable, temperature-independent voltage references. As the critical dimensions of integrated circuits have decreased over time, the operating voltages of these integrated circuits have also decreased. With the decrease in operating voltages of integrated circuits, the need for temperature-independent voltage reference circuits with low operating voltages has increased. Many of these voltage reference circuits provide a stable reference voltage output while operating at voltages at or below 1.3V.
One of the ways to reduce the costs associated with the manufacture of integrated circuits involves limiting the area used to implement circuits within the integrated circuit. In general, circuits that are less complex and require less area to implement are less expensive to manufacture. Further, by reducing the area required to implement some of the circuits within an integrated circuit, it may be possible to reduce the overall size of the integrated circuit, permitting the integrated circuit to be incorporated into smaller devices.